The invention is based on a method for producing sterile packages. In order to avoid using chemical sterilizing agents in producing containers for sterile packaging of perishable foods, a method is already known from German Offenlegungsschrift 27 44 506, in which a multi-layered strip composed of a strip of packaging material and a protective strip covering the inside thereof is prepared for the container and another for the lid; the two sides of the two layers resting on one another are kept sterile. In a sterile enclosure in which cup-shaped containers are shaped and filled, the two layers are peeled apart. One strip of packaging material is then shaped into containers, and after the containers are filled the covering strip is then sealed onto the containers. The protective strips, after being peeled off, are wound up again and put through a recycling process. For one example, it was proposed that the protective strip be used as a covering foil for the containers.
This known method necessitates some precautions which are difficult to adhere to. For instance, the protective strip must be joined to the packaging material strip under sterile conditions. Also, the bond should be arranged such that the protective strip can be easily peeled from the strip of packaging material. On the other hand, if the protective strip is to be used as a covering foil, it must be able to form a good seal with the packaging material strip. This means there are limitations in terms of the attainable tightness of the sealed seam. Also, the protective strip must not be too thin, to assure that the peeling process works properly. The amount of material required is accordingly relatively large. Since the individual layers must be joined to one another under sterile conditions, preferably immediately after their manufacture, it is hardly possible to provide for printing of the protective strip, and so it can hardly be considered for use as a covering foil. Also, it is very expensive to manufacture the strips, because this requires a very special starting material, which is shaped into a strip under controlled, sterile conditions.
A further disadvantage is that the packager of the product loses the opportunity to oversee securing the sterility of the packaged product at several points. Specifically, the strips can become contaminated during manufacture, printing, cutting, transporting, and storage. In particular, an unintentional delamination at the cut side edges can occur during these various operations, causing a local contamination. For this reason, in practice the protective strip that is to be peeled off is slit at a distance of approximately 1 cm from the edge, so that the vulnerable outer zone is not sent to the processing station or stations. As a result, however, there is still further waste.
A method for producing sterile packages in two parts is also known from German Offenlegungsschrift 30 19 503, in which a tube of packaging material having a sterile inside surface is furnished, folded flat, and as it enters the sterile enclosure it is cut into two strips at its two folded edges. Depressions are formed in one of these strips and the depressions are filled, and then the other strip is sealed onto the first, that is, the strip having the depressions. In this process, the wall of the tube may be quite thin, because the sterility in the interior of the tube can readily be maintained. In order to lend the containers a certain rigidity, the strip having the depressions may have an underlay of a separate deformable strip, which is then deformed together with the one strip of the tube. This method has the advantage over the first method described above in that a substantially less expensive, standard material can be used as the starting material, that the sterility in the interior of the tube can be attained substantially more easily than is the case with flat material, and that a loss in sterility during storage and transporting is much less likely, because the tube is closed on the side. Furthermore, underlaying the strip having the depressions with an additional deformable strip is also advantageous if, in the case where printing might be done, it is not the strip having the depressions itself, but rather the additional strip that will be printed upon. The disadvantage of this packaging manufacturing method known from German Offenlegungsschrift 30 19 503, however, is that after the tube has been separated into two strips, the strip intended for sealing must be transported over a relatively long distance, bridging over the stations for forming and filling the depressions, and care must be taken that the sterile inner surface not be infected from the direction of the non-sterile outer surface.